Iron is essential for several vital biological processes. Its deficiency or overload drives to the development of several pathologies. To maintain iron homeostasis, the organism controls the dietary iron absorption by enterocytes, its recycling by macrophages and storage in hepatocytes. These processes are mainly controlled by hepcidin, a liver-derived hormone which synthesis is regulated by iron levels, inflammation, infection, anemia and erythropoiesis. Besides the systemic regulation of iron metabolism mediated by hepcidin, cellular regulatory processes also occur. Cells are able to regulate themselves the expression of the iron metabolism-related genes through different post-transcriptional mechanisms, such as the alternative splicing, microRNAs, the IRP/IRE system and the proteolytic cleavage. Whenever those mechanisms are disturbed, due to genetic or environmental factors, iron homeostasis is disrupted and iron related pathologies may arise.

Nonsense-mediated mRNA decay (NMD) is a surveillance mechanism that degrades mRNAs containing premature translation termination codons. In mammalian cells, a termination codon is ordinarily recognized as "premature" if it is located greater than 50 -54 nucleotides 5 to the final exon-exon junction. We have described a set of naturally occurring human ␤-globin gene mutations that apparently contradict this rule. The corresponding ␤-thalassemia genes contain nonsense mutations within exon 1, and yet their encoded mRNAs accumulate to levels approaching wild-type ␤-globin (␤ WT ) mRNA. In the present report we demonstrate that the stabilities of these mRNAs with nonsense mutations in exon 1 are intermediate between ␤WT mRNA and ␤-globin mRNA carrying a prototype NMD-sensitive mutation in exon 2 (codon 39 nonsense; ␤39). Functional analyses of these mRNAs with 5-proximal nonsense mutations demonstrate that their relative resistance to NMD does not reflect abnormal RNA splicing or translation re-initiation and is independent of promoter identity and erythroid specificity. Instead, the proximity of the nonsense codon to the translation initiation AUG constitutes a major determinant of NMD. Positioning a termination mutation at the 5 terminus of the coding region blunts mRNA destabilization, and this effect is dominant to the "50 -54 nt boundary rule." These observations impact on current models of NMD.Nonsense-mediated mRNA decay (NMD) 1 is an mRNA surveillance mechanism that rapidly degrades mRNAs carrying premature translation termination codons (1). Nonsense-containing mRNAs targeted by NMD can be generated by naturally occurring frameshift and nonsense mutations, splicing errors, leaky 40 S scanning, and utilization of minor AUG initiation sites (2, 3). A major function of the NMD pathway is to block the synthesis of truncated proteins that could have dominant negative effects on cell function (2, 4).Recent studies have shown that the NMD pathway in mammalian cells is linked to splicing-dependent deposition of a protein complex 20 -24 nucleotides (nt) 5Ј of each exon-exon junction (exon-junction complex; EJC). The EJC contains the general splicing activator RNPS1, the RNA export factor Aly/ REF, the shuttling protein Y14, the nuclear matrix-localized serine-arginine-containing protein SRm160, the oncoprotein DEK, and the Y14 binding protein magoh. The interaction of magoh with Y14 may have a role in cytoplasmic localization of mRNAs and in anchoring the NMD-specific factors Upf3 and Upf2 to the mRNA (5-18). Previous published data have shown that Upf3 and Upf2 join the EJC in different subcellular compartments: Upf3 (Upf3a and Upf3b) is loaded onto mRNAs in the nucleus during splicing via interactions with components of the EJC. In contrast, Upf2 joins the complex soon after cytoplasmic export is initiated (14,19,20). According to the present models, translating ribosomes displace EJCs from the open reading frame (ORF) during the "pioneer" round of cytoplasmic translation (21). If, however, the mRNA contains a pr...

We developed a series of interrelated locus-specific databases to store all published and unpublished genetic variation related to these disorders, and then implemented microattribution to encourage submission of unpublished observations of genetic variation to these public repositories 1. A total of 1,941 unique genetic variants in 37 genes, encoding globins (HBA2, HBA1, HBG2, HBG1, HBD, HBB) and other erythroid proteins (ALOX5AP, AQP9, ARG2, ASS1, ATRX, BCL11A, CNTNAP2, CSNK2A1, EPAS1, ERCC2, FLT1, GATA1, GPM6B, HAO2, HBS1L, KDR, KL, KLF1, MAP2K1, MAP3K5, MAP3K7, MYB, NOS1, NOS2, NOS3, NOX3, NUP133, PDE7B, SMAD3, SMAD6, and TOX) are currently documented in these databases with reciprocal attribution of microcitations to data contributors. Our project provides the first example of implementing microattribution to incentivise submission of all known genetic variation in a defined system. It has demonstrably increased the reporting of human variants and now provides a comprehensive online resource for systematically describing human genetic variation in the globin genes and other genes contributing to hemoglobinopathies and thalassemias. The large repository of previously reported data, together with more recent data, acquired by microattribution, demonstrates how the comprehensive documentation of human variation will provide key insights into normal biological processes and how these are perturbed in human genetic disease. Using the microattribution process set out here, datasets which took decades to accumulate for the globin genes could be assembled rapidly for other genes and disease systems. The principles established here for the globin gene system will serve as a model for other systems and the analysis of other common and/or complex human genetic diseases.

There is a strong case for pan-European collaboration on haemoglobin disorders to share policies, standards and the instruments required to support them. These include methods for needs assessment, service standards, education and information strategies and materials, and methods for evaluating service delivery.

β-Thalassemia is one of the most common inherited anemias, with no effective cure for most patients. The pathophysiology reflects an imbalance between α- and β-globin chains with an excess of free α-globin chains causing ineffective erythropoiesis and hemolysis. When α-thalassemia is co-inherited with β-thalassemia, excess free α-globin chains are reduced significantly ameliorating the clinical severity. Here we demonstrate the use of CRISPR/Cas9 genome editing of primary human hematopoietic stem/progenitor (CD34+) cells to emulate a natural mutation, which deletes the MCS-R2 α-globin enhancer and causes α-thalassemia. When edited CD34+ cells are differentiated into erythroid cells, we observe the expected reduction in α-globin expression and a correction of the pathologic globin chain imbalance in cells from patients with β-thalassemia. Xenograft assays show that a proportion of the edited CD34+ cells are long-term repopulating hematopoietic stem cells, demonstrating the potential of this approach for translation into a therapy for β-thalassemia.